Reclamation of battery plate scrap



Patented Aug. 4, 1936 Y f UNITED STATES PATENT OFFICE RECLAMATION OFBATTERY PLATE SCRAP Alfred M. Thomsen, San Francisco, Calif assignor toThomsen Chemical Corporation, a corporation of California I No Drawing.Application February 24, 1933,

7 Serial No. 658,447,

4 Claims. '(Cl. 75 -77) This application is a continuation in part of'continuously or intermittently. It will be 'eviapplication Serial No.609,765, filed May 6, 1932. dent that the charge is kept in a state ofcon The development of the storage battery has tinuous agitation bythemotion of the roaster, given rise to a new form'of industrial waste,-and thus every opportunity is given the globules 5 namely, old batteryplates. Such battery plates 7 of molten 'metal to sift downwards andjoin are really a mixture of two different substances; the pool of suchmolten metal which gradually the metallic grid, which is composed ofantiforms at theitalus of the sliding, unmelted' parmonial lead, and thepaste, with which the ticles, drawn up to the properangle of slip by thegrid is filled. Such paste is composed of a mixmotion of the'roaster.

10 ture of the oxides and sulphates of lead, and Having thus separatedthe fusible from the 10 it is'entirely free from antimony. Direct blastinfusible portion of the charge, the temperature furnace smelting ofthis kind of a mixture can, is raised to the point at which the sulphurcomof course, only result in the recovery of a low pounds are brokendown with-the formation of antimony alloy,'for, as the ingredientsdescribed lead oxide, andthe operation continued as a W are present inabout equal proportions, it follows roasting step until only crudelitharge remains 1:;

that the resultant metal will only contain half in .the roaster. of theantimony required to qualify as anti- Manifestly, it is impossible toseparate the monial lead. V metallic portion from the non-metallicportion The customary reclamation practice of to-day of battery plateswith absolute precision by the is to charge the plates into a oupola,and to smelt procedure thus far described. A small amount 20 them, withcoke as fuel, into a low-grade, imof shots, or globules, of antimoniallead will be pure antimonial lead. This operation is attended retainedin the pulverulent residue remaining by much loss, and virtually putsthis high-grade in the furnace, and this metal will in the roastmaterialin the same class as an undesirable antiing step, as previouslydescribed, be converted monial lead ore. In order to purify theresultant. into oxide. The crude litharge will therefore 25 low-grademetal obtained from present day contain a certain small percentage ofantimony practices, it must be liquated at least once, if oxide. Shouldit be desirable torender this pernot twice, drossed, oxidized, andreduced. It centage as small as possible, then the pulverumust then bebrought up to market standards lent residue, remaining after'theliquation of all by the addition of the requisite amount of metalthemetal that may be drawn from the furnace, 3O lic antimony,-all of whichmeans considerable is discharged, cooled, and passed through a mill, I

expense. such as a set of rolls, or a rod mill. As the My improvedprocess varies radically from 'paste is very brittle, the effect of themill these present day practices; to elucidate: will be to reduce it toa powder. And as the 5 If we consider the difference in melting pointshots of lead, in spite of their antimony conbetween the metal portionand the paste, we tent, are still somewhat malleable, they will findthat the metal fuses at below 350 C., that flattenif not too harshlytreated. The ground lead oxide fuses at about 900 C., and leadsulresidue may therefore undergo a further puriphate at over 1100 C. Itis therefore evident fication by means of screening,-most of the 4 thatif the material be heated to a temperature mechanically admixedantimonial lead being re- 40 intermediate between these extremes, thenthere tained upon the screen, while the undersize will will be effecteda separation between the paste be. almost free from antimony. Thefurther and the metallic portion. Furthermore, as the roasting of thisundersize tocrude litharge will specific gravity of the metal is over11, and the be much facilitated by the fact that it is now specificgravity of the paste somewhere bein the form of a line powder, and theroasting i5 tween 9 (for lead oxide) and 6 (for lead sultime willtherefore be much shortened. phate), depending upon the relativequantities The breaking up of sulphates in this roasting of thesesubstances present, it will be evident, is aided by the presence ofcarbon (such asis also, that the tendency of the lead will be to alreadypresent as charcoal from plate separatsettle to the bottom, and for thepaste to ors), but additional carbon may be added. The e0 float on topof the melted lead. action of this carbon is to reduce the sulphate Tocarry out this step I prefer the use of a to s ph de, which in turn thenexercises a, re-

revolving roaster, in which the solid oxidized ducing action on leadoxide. Such reduced lead lead compounds may readily be retained whilethe will soon be re-oxidized to litharge, and the sulmobile fused leadis allowed to flow away, either phur has thus been eliminated. s5

Of course, I may avoid the use of the cupola altogether if I now addsufficient carbon in some form (coke, coal charcoal, etc.), to thecharge Within the revolving roaster.- This will reduce sulphate tosulphide which in turn will reduce the oxide with which the sulphide isin contact, and the oxide itself will likewise be reduced thereby. 11may -,thus obtain most of the lead of the charge-in the form of puresoftlead,'eliminating at once the need for the cupola, the drossing furnace,and the softening kettle.

The type of work described in :the last ,two paragraphs is a modernversion of Die Roestre-aktions-Arbite, which, in English -is bettergiven by the term roast-reduction, employed in the claims. For fulldescription, reference is made to any work on metallurgy which devotesspace to old fashioned procedures-such -:a;s Hofimans Metallurgy ofLead, where, in the seventh impression, chp. 6, we are given a fullexposition of reverberatory furnace practice in lead ores. 1tWill;be:se1f-;evidentithat theaddition of carbon. above referred to,toia ;residual of lead sulphate and oxide :will be entirely .inaccordance with {the ;description.. Whenever in the claims theexpression ".froastereduction :is used it, means ,that combination ;ofoxidation and reduction as described in the e-aboveementioned chapter.

H v n thus described improvement, I claim:

1. A process for separating the fused metallic from the unfusednon-metallic constituents .-of battery plate, which comprises firstheating the material to be treated to a temperature sufficient to fusethe metallic alloy but insuflicienttomelt tion, said liquation beingeffected by heating 'the .charge,contained within a revolving roaster,to

a sufficiently high temperature to fuse the metallic ingredient whilethe non-metallic ingredients remain unfused, and submitting the furnaceresidue to the operation of grinding and screening .for a more thoroughseparation, substantially as and in the manner indicated.

3. In the process of reclaiming battery plate scrap, the step ofseparating the fused metallic fromm'the... non-rinsedv non-metallicingredient withinaairevolving roaster, removing the, fused metallicingredient, and eliminating the sulphate-sulphunin :the;residue throughthe additionnf carbonaceous material by roast-reduction treatment. b V

zihinttherprooess of reclaiming-battery plate scrap, ithestep ofremoving the major portion of antimony there in ;the form of ,antimoniallead byiusion, fol-lowed hyla further removal of part 1 Qfzthesremaininglantimonial lead by grinding and..-screening, submitting-the residue toroastreduction treatment, andsoftening the lead thus produced to obtainthe remaining antimony in theform of ,antimonial litharge.

ALFRED 1M. THOMSEN.

